1. Field of the Invention
This invention relates generally to a process and apparatus for forming a corrugated substructure and, more specifically, to such a process and apparatus for rapidly and economically forming a corrugated substructure which is of complicated shape.
2. Description of the Prior Art
For many years, aluminum honeycomb has been utilized as a very strong, yet light weight, substructure for the construction of airfoils and other airfree components of high performance aircraft.
Unfortunately, aluminum honeycomb has been identified as one of the major sources of corrosion problems in older designs. At the same time, the use of aluminum honeycomb in aircraft construction is labor intensive by reason of the substantial amount of machining which is required in order to properly shape the honeycomb to the necessary aircraft contours.
An important recent technological achievement has been the development of corrugated cores of graphite composite material. Such materials have the desirable characteristics of aluminum honeycomb including lightweight and strength, but have the added benefit of not being subject to corrosion. However, as with aluminum honeycomb, until the present time, the fabrication of the graphite corrugated substructure has been limited to hand layup methods which are themselves labor intensive.
Efforts to automate the continuous production of corrugated material have achieved some measure of success as exemplified by the U.S. patents to Oesterheld, No. 3,170,192, issued Feb. 23, 1965 and to Bush, No. 3,540,079, issued Jan. 30, 1968. According to Oesterheld, soft fresh sheets of fibrous cement are passed over corrugations in the cover of a suction box at approximately uniform speed. Suction in the suction box serves to draw the cement downwardly against the corrugations of the cover of the suction box. After the sheet has been thus formed, it is removed to be set and cured such that the corrugations are permanently formed in the sheet material.
The Bush machine operates to corrugate continuous sheets of pliable material such as plastic, paper, metal foil, or certain textiles. As with Oesterheld, a vacuum draws the sheet being corrugated downwardly into firm engagement with a plurality of spaced ribs over which it is drawn. The transverse spacing of the ribs is variable and when the spacing is reduced to a minimum the sheet is drawn to the area between the adjacent ribs to form the corrugations.
However, such known techniques apply to the production of regularly shaped and repeatable corrugated designs. In contrast, the techniques which are disclosed herein are directed toward the fabrication of highly irregular shapes which, by reason of their irregularity, had previously required totally manual handling which, at best, utilized jigs and fixtures applicable only to a portion of the procedure.